1. Technical Field
The present invention relates to a motor.
2. Description of the Related Art
A spindle motor, which is used in a driving device of a large-capacity memory storage device such as an optical disk, an ODD slim and a Half height driving set, uses an oil-impregnated bearing to help a shaft to rotate. The oil-impregnated bearing is a kind of a sliding bearing, and is made of a porous material that can contain lubricating oil. The porous material commonly consists of a sintered body.
The oil-impregnated bearing is joined to the shaft such that there exists a constant gap therebetween. The gap is filled with lubricating oil leaked from the oil-impregnated bearing due to the rotation of the shaft. The oil-impregnated bearing can hereby support the shaft to be rotatable.
However, the lubricating oil contained in the oil-impregnated bearing can be leaked not only to the gap between the shaft and the bearing but also to the upper part of the oil-impregnated bearing. When the lubricating oil of the oil-impregnated bearing is lost, the lubrication of the oil-impregnated bearing is deteriorated and a friction between the shaft and the oil-impregnated bearing is increased.
Accordingly, more power is required for driving the spindle motor, and noise and vibration and the like may occur when the motor rotates at a high speed. Besides, some parts of the bearing may be also worn out due to the friction between the shaft and the oil-impregnated bearing, thereby causing a shorter life span of the spindle motor.